Indole-3-pyruvate is a strong antioxidant that is believed to counter act oxidative stress in tissues with high oxygen concentrations (Politi et al. “Recent advances in Tryptophan Research”, edited by G. A. Filippini et al. Plenum Press, New York, 1996, pp 291-8). Indole pyruvate also is an intermediate in a pathway to produce indole-acetic acid (IAA), the primary plant growth hormone auxin (diffusible growth promoting factor). IAA is active in submicrogram amounts in a range of physiological processes including apical dominance, tropisms, shoot elongation, induction of cambial cell division, and root initiation. Synthetic auxins are used in horticulture to induce rooting and to promote the set and development of fruit. See, e.g., U.S. Pat. Nos. 5,843,782 and 5,952,231. At high concentrations the synthetic auxins are effective herbicides against broad-leafed plants. Natural auxins produced by fermentation may be considered more environmentally friendly than chemically produced herbicides. Growth regulators had world sales in 1999 of 0.4 billion pounds (1.4 billion U.S. dollars). In addition to plant related utilities, indole acetic acid is useful in pharmaceutical applications. For example, U.S. Pat. No. 5,173,497 proposes the use of these compounds in the treatment of memory impairment such as that associated with Alzheimer's disease and senile dementia. The mechanism proposed in U.S. Pat. No. 5,173,497 is that these compounds inhibit acetylcholinesterase and increase acetylcholine levels in the brain.
Indole-3-carbinol is produced from indole-3-acetic acid by peroxidase-catalyzed oxidation, and can easily be converted into-diindolylmethane. Both compounds are reported to eliminate toxins and promote the production of hormones beneficial to women's health. Chlorinated D-tryptophan has been identified as a nonnutritive sweetener, and there is increasing interest in pursuing other derivatives as well.
Monatin (2-hydroxy-2-(indol-3-ylmethyl)-4-aminoglutaric acid) is a naturally-occurring, sweetener that is similar in composition to the amino acid tryptophan. It can be extracted from the bark of the roots of the South African shrub, Sclerochiton ilicifolius, and has promise in the food and beverage industry as a high-intensity sweetener. Some examples of patents on monatin include: U.S. Pat. Nos. 5,994,559; 4,975,298; 5,128,164; and 5,128,482.